In conventional automotive alternators, an inboard bearing and an outboard bearing are disposed at two ends of a shaft in order to support a rotor, the inboard bearing is fixed to an inboard bracket by being press-fitted directly into the inboard bracket and fastening a retainer using screws, the outboard bearing is not fixed to an outboard bracket using a retainer, a resin spacer is disposed between a bearing housing portion of the outboard bracket and a bearing outer ring in order to prevent coupling strength between the bearing housing portion and the bearings from decreasing due to differences in thermal expansion between the two that result from heat generated during the driving of the automotive alternator, and the outer ring of the bearing is prevented by the spacer from rotating relative to the bearing housing portion (see Patent Literature 1, for example).